I don't know what nutrients you might be missing from peanut butter. A lot of my cravings are for foods with no nutritional value.
I've found a couple tricks that work for me with cravings. I tell myself I can have it if I still want it in 2 hours (or 30 minutes, or even 10 minutes). The problem with that is even though I'm no longer craving it 2 hours later, I feel cheated so I have it anyway. So that doesn't always work.
Another trick I learned recently is to imagine myself eating that food. This is based on a study where participants imagined themselves eating 5 M&M's, 30 M&M's, or nothing. Then they were given a bowl of M&M's. The people who imagined eating 30 M&M's ate half as many M&M's as the other 2 groups. This one works better for me because imagining it distracts me from the craving, and then I don't get that cheated feeling.
That might work better if you are naturally gullible. Like me.
2009 Trek 7.2FX WSD, brooks Champion Flyer S, commuter bike